Process of improving the quality of mason&#39;s hydrated lime



PATENT OFFICE.

rumors C. WELO H OI BEVERLY, IASSACHUSETTE 330cm; or mrnovmo THE 1,410,087. No Drawing Specification of Letters Patent QUALITY OF IASONS HYDBATE .LIIE.

' Patented Mal-.21, 1922.

Application filed ll'ovember 8, 1921,. Serial). 518,888.

nun mum; an m or mum]: 3.1m, 2:: sum. LL, 02s.

To all whom it may concern:

Be it known-that I, FRANCIS 0. Wm, a citizen of the United States, residing at Beverly, in the State of Massachusetts, I have 5 invented new and useful Improvementsin v the Processes of Improving the Quality of Masons Hydrated Lime, of which the following is a specification:

This application is filed under the act of 0 March 3, 1883, under the terms of which, the

applicant. agrees that the invention described herein, if patented, may be used by the Government or any of its ofiicers or em-' ployees in prosecution of work for the Gov- '15 ernment, or by any other persons in the United States without the payment tohim. of any royalty thereon.

Masons hydrated lime is completely defined by the specifications for same, isued go by the American Society for TestingMaterials, No. C621T. In these specifications, the distinction between masons and finishing hydrate is based solely upon the lastic1ty: for finishing hydrate, theplasticity figure must be greater than 200. Practically, the two kinds of hydrate are distinguished by the fact that masonshydrate cannot be used for the finishing coat of plaster. It is 'so lacking in plasticity that the plasterer cannot spread it on the wall.

The evidence indicates that both kinds of hydrate consists mainly of particles of colloidal size, the diflerence being'that in the finishing hydrate, these particles may be readily separated from each other, while in the masons hydrate, they are aggregated together in groups. Each oup ofi particles is apparently surrounded y an envelope of water, and the cohesion between the particles 40 in a group is so strong that the group cannot be broken up into. its component particles, even by the most severe grinding.

I find that if masons hydrate is ground either in the presence of or mixed with a drying agent, the drying agent destroys the water envelopes surrounding the groups, and the grinding then breaks down the groups into individual particles. This results in an improvement of plasticity such that a masons hydrate, so treated, can be used as a finishinghydrate.

As drying agents, I have found efi'ective the followin materials, but it is obvious that any materia s of similar'nature" will answer the purpose; those which absorb the water physically slate, shale, kaolin, diatomaceous earth, tripoli, fine sand, clay; those which absorb the water chemically, calcined gypi sum, quicklime, magnesia, or the oxides of barium, iron, and phosphorus.

As this operation depends upon the breaking up of the water envelope surrounding the groups of particles in the masons hydrated lime, and the water comprising these envelopes hasa certain definite vapor pressure depending upon its temperature, the desired results can also be obtained by increasing the temperature of the hydrate or by increasing the temperature or lowering the humidity of a current of air passed over the. hydrate.

By heating the hydrate .or by increasing the temperature or lowering the humidity of a current of air passed over the hydrate, the vapor pressure. of the envelope of water around the particles of the hydrate is greater than the vapor pressure of the water in the air, causing the waterenvelope to evaporate.

The quantity of drying agent whichmay be added dependssomewhat upon economic conditions. I have achieved satisfactory results with as low as one per cent by weight of the hydrate. Equally d resultscan be obtained with larger additions of material, according tothe dehydrating power and amount of grinding u to the point where the added material seriously affects the set-- ting properties of the lime.

The duration of grinding depends upon the type of equipment used, the power and quantity ofthe dehydrating agent and the de ofplasticity required.

' pecifically, I find that if to a masons hydrate is added one per cent of its weight of quicklime and the mixture ground 1n a ball mill for 2 hours, the resultant product will be sufficiently plastic to meet the IQtitlll'fl ments for finishing hydrate (see A. S. M. specification cited above).

1. The process of increasing the plasticity of masons hydrated lime, which comprises the grindingv of the masons hydrated lime in contact with a drying agent. o 2. The process of increasin the plasticity of masons hydrated-lime, w ich comprises the grinding of the masons hydrated lime,

with an admixture of a material which can the plasticity hydrated lime, which comprises 'of mason ich comprises the grinding of the masons hydrated lime with an admixture of quick lime.

6. The process of increasing the plasticity s hydrated lime w ich comprises the grinding of the masons hydrated lime in a current of warm, dry air.

7. The process of increasing the plasticity of mason s hydrated lime, which comprises grinding in a current of air the masons hydrated limeat a. temperature whereby the water in the hydrate is partially evaporated.

FRANCIS C. WELCH. 

